advanced attribute selectors

    [class^=col-] { /* start with col- */ }

    [class$=col-] { /* end with col- */ }

    [class*=col-] { /* contain with col- */ }

calc & not psudo selector

    $gutter_horizontal: 80px;

    .col-1-of-2 { /* grid col-1-2 */
        width: calc(( 100% - $gutter_horizontal) / 2 );
        &:not(:last-child) {
            margin-right: $gutter_horizontal;
        }
    }